A laminated glass is a safety glass which, even when broken by impact from the outside, shatters into few flying glass fragments. For this reason, a laminated glass is widely used for cars, rail cars, aircrafts, boats and ships, buildings, and the like. The laminated glass is produced by sandwiching an interlayer film for a laminated glass between a pair of glass plates.
Patent Document 1 provides one example of the interlayer film for a laminated glass; that is, Patent Document 1 teaches a sound insulation layer that contains 100 parts by weight of a polyvinyl acetal resin having a degree of acetalization of 60 to 85 mol %, 0.001 to 1.0 part by weight of at least one metal salt of an alkali metal salt and an alkaline earth metal salt, and 30 parts by weight or more of a plasticizer. This sound insulation layer alone can be used as an interlayer film.
Patent Document 1 also teaches a laminated interlayer film in which the sound insulation layer and other layers are laminated. Each of the other layers laminated on the sound insulation layer contains 100 parts by weight of a polyvinyl acetal resin having a degree of acetalization of 60 to 85 mol %, 0.001 to 1.0 part by weight of at least one metal salt of an alkali metal salt and an alkaline earth metal salt, and 30 parts by weight or less of a plasticizer.    Patent Document 1: JP 2007-070200 A